Recording method and apparatus for continuous playback of fragmented signals

ABSTRACT

By reducing the number of seek operations in an operation to play back a signal from a recording medium, the amount of data temporarily stored in a read buffer memory employed in a signal recording/playback apparatus is large enough to be output as a playback signal during a seek operation, allowing a continuous playback operation to be carried out. In order to reduce the number of seek operations, a signal is always recorded onto the recording medium in continuous free areas each having a size equal to or larger than a predetermined recording/playback time length which is typically set at 1 minute. If it is necessary to insert an additional signal having a length smaller than the predetermined recording/playback time length into a point of insertion in an area already occupied by an existing signal, a continuous free area with a size equal to or larger than the predetermined recording/playback time length is newly allocated to the additional signal. The additional signal is then recorded in the free area instead of being inserted into the point of insertion. Since the free area is larger in size than the length of the additional signal, the rest of the free area is filled up with a portion of the existing signal adjacent to the point of insertion.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a technology for recording andplaying back signals such as video and audio signals into and from anerasable recording medium such as an optical magnetic disc, a variablephase disc and a magnetic disc.

[0002] By virtue of development of band compression technologiesrepresented by the recently introduced MPEG (Moving Picture ExpertsGroup) compression/coding technology, signals such as audio and videosignals can now be recorded into a large capacity recording medium suchas an optical magnetic disc for a playback operation of a long time.

[0003] When a signal is recorded into such a recording medium, thesignal undergoes a band compression/coding process, being recorded insector units. The signal is then recorded into free areas on therecording medium.

[0004] Traditionally, a signal continuous in the time axis directionresulting from typically editing work such as an audio or video signalis recorded into a recording medium, being split into segments as shownin FIG. 21 (1). In the figure, the symbol # on each of the segmentsindicates the order number in an operation to play back the signal.While the segments of the signal are arranged along a straight line asshown in the figure, the signal is actually recorded on a track having aspiral shape or concentric tracks on the recording medium.

[0005] Consider a playback operation in which segment #5 is reproducedafter segment #4. In this case, a reproduced signal generated by a readpickup is broken due to a seek time, a rotation wait time and a settletime which are required between segments #4 and #5. The seek time is aperiod of time it takes to move the read pickup in a so-called trackjump to a track in area where segment #5 is recorded. On the other hand,the rotation wait time is a period of time it takes to wait for the readpickup to arrive at the position of a target sector on the track.Finally, the settle time is a period of time it takes the tracking servoof the read pickup to get settled.

[0006] In order to prevent a playback signal eventually generated by therecording/playback apparatus from being broken even if the reproducedsignal generated by the read pickup is unavoidably broken as describedabove, a read buffer memory is provided for storing in advance a signalread out from the recording medium. The signal stored in the read buffermemory is used for filling up the time gap between two consecutivesegments, that is, a period of time during which no reproduced signal isgenerated by the read pickup. The signal stored in the read buffermemory is then output when the reproduced signal generated by the readpickup is broken.

[0007] In the case of a recorded signal split into a large number ofsegments as shown in FIG. 21 (2), however, it is quite within the boundsof possibility that the amount of data stored in advance in the readbuffer memory during the time is not large enough to be used for fillingup a time gap between two consecutive segments. As a result, theeventual playback signal can not be generated continuously.

SUMMARY OF THE INVENTION

[0008] The present invention addresses the problems described above. Itis thus an object of the present invention to provide a technology thatmakes a continuous playback operation possible by assuring that theamount of data stored in a read buffer memory is large enough foreliminating a playback time break through reduction of the number ofseek operations.

[0009] In order to achieve the object of the present invention, thepresent invention provides a signal recording method whereby, in anoperation to record a signal onto a recording medium, the signal isrecorded in continuous free areas each having a size equal to or largerthan a predetermined recording/playback time length.

[0010] In addition, the present invention also provides a signalrecording/playback method wherein, in an operation to insert anadditional signal having a length smaller than a predeterminedrecording/playback time length into a point of insertion in an area on arecording medium already occupied by an existing signal, the signalrecording/playback method is implemented by executing the steps of:

[0011] newly allocating a continuous free area on the recording mediumwith a size of at least the equivalence of the predeterminedrecording/playback time length to the additional signal;

[0012] recording the additional signal in the continuous free area; and

[0013] filling up the rest of the continuous free area with a portion ofthe existing signal adjacent to the point of insertion.

[0014] Furthermore, the present invention also provides a signalrecording/playback method wherein, in case a signal already recorded ona recording medium has a continuous segment smaller in size than anequivalence of a predetermined recording/playback time length, thesignal recording/playback method is implemented by executing the stepsof:

[0015] newly allocating a continuous free area on the recording mediumwith a size of at least the equivalence of the predeterminedrecording/playback time length to the segment;

[0016] relocating the segment to the continuous free area; and

[0017] filling up the rest of the continuous free area with a portion ofthe signal adjacent to the segment.

[0018] On the top of that, the present invention also provides a signalrecording apparatus for recording a signal onto a recording medium, theapparatus comprising:

[0019] a 1st means for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0020] a 2nd means for executing control to record a signal onto thecontinuous free area.

[0021] In addition, the present invention also provides a signalrecording/play back apparatus for recording and playing back a signalonto and from a recording medium, the apparatus comprising:

[0022] a 1st means for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0023] a 3rd means for executing control to record a signal, which issupposed to be newly inserted into a point of insertion in an area onthe recording medium already occupied by an existing signal, onto thecontinuous free area and to fill up the rest of the continuous free areawith a portion of the existing signal adjacent to the point ofinsertion.

[0024] Furthermore, the present invention also provides a signalrecording/play back apparatus for recording and playing back a signalonto and from a recording medium, the apparatus comprising:

[0025] a 1st means for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0026] a 4th means for executing control to relocate a continuoussegment of a signal already recorded on the recording medium having asize smaller than a predetermined recording/playback time length and tofill up the rest of the continuous free area with a portion of thealready recorded signal adjacent to the segment.

[0027] On the top of that, the present invention also provides a signalrecording medium wherein a signal is recorded into continuous areas eachhaving a size equal to or larger than a predetermined recording/playbacktime length.

[0028] According to one aspect of the present invention, there isprovided a signal recording apparatus provided for recording a signalonto a recording medium wherein:

[0029] a 1st means is used for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0030] a 2nd means is used for executing control to record a signal ontothe continuous free area.

[0031] In addition, according to another aspect of the presentinvention, there is provided a signal recording/play back apparatus forrecording and playing back a signal onto and from a recording mediumwherein:

[0032] a 1st means is used for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0033] a 3rd means is used for executing control to record a signal,which is supposed to be newly inserted into a point of insertion in anarea on the recording medium already occupied by an existing signal,onto the continuous free area and to fill up the rest of the continuousfree area with a portion of the existing signal adjacent to the point ofinsertion.

[0034] On the top of that, according to a further aspect of the presentinvention, there is provided a signal recording/play back apparatus forrecording and playing back a signal onto and from a recording mediumwherein:

[0035] a 1st means is used for recognizing a continuous free area on therecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and

[0036] a 4th means is used for executing control to relocate acontinuous segment of a signal already recorded on the recording mediumhaving a size smaller than a predetermined recording/playback timelength and to fill up the rest of the continuous free area with aportion of the already recorded signal adjacent to the segment.

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] An embodiment of the present invention will be described byreference to the following diagrams wherein:

[0038]FIG. 1 is a block diagram showing the configuration of a signalrecording/playback apparatus to which the present invention is applied;

[0039] FIGS. 2 (1) and (2) are diagrams each showing a layout of asignal on a disc undergoing an operation to record an additional signalportion carried out by the signal recording/playback apparatus onto thedisc;

[0040]FIG. 3 is a diagram showing locations of 3 programs recorded in 3files on the disc with locations of each of the files represented by astraight line pattern;

[0041]FIG. 4 is a table showing an example of file system controlinformation comprising entries to be referenced by a file system;

[0042]FIG. 5 shows an example of a FAT (File Allocation Table);

[0043]FIG. 6 is a diagram showing a technique for implementing controlof a fixed rate to be achieved in a 1-minute period of time;

[0044]FIG. 7 is a block diagram showing the configuration of anapparatus implementing the fixed rate control;

[0045]FIG. 8 shows a flowchart representing an encoding process forimplementing the fixed rate control;

[0046] FIGS. 9 (1) to 9 (5) are diagrams showing layouts of a signalrecorded on the disc of the signal recording/playback apparatus shown inFIG. 1 in an editing process;

[0047] FIGS. 10 (1) and 10 (2) are diagrams showing general optimizationof a signal;

[0048] FIGS. 11 (1) to 11 (5) are diagrams showing general optimizationof a signal carried out in the embodiment;

[0049]FIG. 12 is a diagram showing a signal to be edited in theembodiment;

[0050] FIGS. 13 (1) to 13 (5) are diagrams showing examples of editingwork carried out on a signal;

[0051] FIGS. 14 (1) to 14 (5) are diagrams showing other examples ofediting work carried out on a signal;

[0052] FIGS. 15 (1) to 15 (4) are diagrams showing still other examplesof editing work carried out on a signal;

[0053] FIGS. 16 (1) to 16 (4) are diagrams showing further examples ofediting work carried out on a signal;

[0054] FIGS. 17 (1) to 17 (5) are diagrams showing still furtherexamples of editing work carried out on a signal;

[0055] FIGS. 18 (1) to 18 (3) are diagrams showing still furtherexamples of editing work carried out on a signal;

[0056] FIGS. 19 (1) to 19 (4) are diagrams showing still furtherexamples of editing work carried out on a signal;

[0057] FIGS. 20 (1) to 20 (3) are diagrams showing still furtherexamples of editing work carried out on a signal; and

[0058] FIGS. 21 (1) and (2) are explanatory diagrams used for describingthe ordinary method to play back a signal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0059] The above and other objects, features as well as many of theattendant advantages of the present invention will become more apparentand, thus, more readily appreciated as the same becomes betterunderstood from a careful study of the following detailed description ofa preferred embodiment of the present invention with reference to theaccompanying diagrams. The description is divided into sections listedbelow which are explained sequentially in the order the sections are puton the following list:

[0060] 1 Configuration of the Signal Recording/Playback Apparatus

[0061] 2 Recording of an Additional Signal

[0062] 3 Recognition of Free Areas

[0063] 4 Editing

[0064] 5 Optimization

[0065] 6 Editing Details

[0066] 1 Configuration of the Signal Recording/Playback Apparatus

[0067]FIG. 1 is a block diagram showing the configuration a signalrecording/playback apparatus to which the present invention is applied.The signal recording/playback apparatus records and plays back video andaudio signals into and from a solid memory represented by an opticalmagnetic disc, a magnetic disc, a magnetic tape and a semiconductormemory in addition to a data recording medium in general by multiplexingthe signals. In order to simplify the description, however, only anoptical magnetic disc which is referred to hereafter simply as a disc isexplained as a representative.

[0068] In this signal recording/playback apparatus, a system controller1 controls the apparatus as a whole in addition to carrying out otherfunctions. A video encoder 2 performs a video encoding process on avideo signal supplied thereto. By the same token, an audio encoder 3carries out an audio encoding process on an audio signal suppliedthereto. A multiplexer 4 multiplexes the outputs of the video and audioencoders 2 and 3. A write buffer memory 5 is used for temporarilystoring the output of the multiplexer 4. A pickup 6 is used for writingthe output of the write buffer memory 5 onto a disc. In addition, thepickup 6 is also used for reading out a playback signal from the discand outputting the signal played back from the disc to a read buffermemory 7 which is used for temporarily storing the signal read out fromthe disc by the pickup 6. A demultiplexer 8 splits the output of theread buffer memory 7 back into video and audio data. A video decoder 9carries out a video decoding process on the video data resulting fromthe split done by the demultiplexer 8. By the same token, an audiodecoder 10 carries out an audio decoding process on the audio dataresulting from the split done by the demultiplexer 8.

[0069] 2 Recording of an Additional Signal

[0070] FIGS. 2 (1) and (2) are diagrams each showing recording a layoutof a signal on a disc undergoing an operation to record an additionalsignal portion by the signal recording/playback apparatus onto the disc.To be more specific, FIG. 2 (1) is a diagram showing a recording layoutprior to the additional recording operation and FIG. 2 (2) is a diagramshowing a recording layout after the additional recording operation. Inthe figures, a portion shown as a thin mesh denotes an area in which thesignal is recorded. As shown in the figure, an additional signal is notsplit into segments to be each recorded into a free area with a lengthsmaller than a predetermined value, typically an equivalent of the1-minute recording/playback time length. Instead, the additional signalis recorded into a continuous free area with a length equal to or largerthan the 1-minute recording/playback time length.

[0071] 3 Determination of Free Areas

[0072] This section explains a means for recognizing a continuous freearea of at least the predetermined typical value, that is, an equivalentof the 1-minute recording/playback time length in length.

[0073] (a) Means for Recognizing Free Areas

[0074] Information on files on the disc is all recorded in a TOC (Tableof Contents) area. At the time the disc is mounted on the signalrecording/playback apparatus, the system controller 1 reads out thisinformation on files from the TOC area and controls the files on thedisc till the disc is taken out from the apparatus. In order to controlfiles on the disc, the system controller 1 is provided with a FAT (FileAllocation Table) 11. The location and attributes such as the number,the recording date & time and the file name of each file on the disc arecontrolled by referencing the FAT 11. The FAT 11 is used for controllingthe information on files in smallest access units, typically sectorunits, used by the system, that is, the signal recording/playbackapparatus for making an access to the disc. It should be noted that, inthis embodiment, 1 sector is 2,048 bytes (or 2K bytes) in size.

[0075]FIG. 3 is a diagram showing locations of 3 programs recorded in 3files on the disc with locations of each of the files represented by astraight line pattern. For example, continuous data of Program 1 isrecorded by splitting the data into 3 segments forming a pattern along astraight line for physical reasons encountered during an operation torecord the data onto the disc.

[0076] As shown in the figure, a file system in the system controller 1controls information on the file of Program 1 by keeping recordsindicating that the data of Program 1 is recorded continuously fromsectors 1 to 7 and then jumps to sector c in the FAT 11. The file systemobtains information on free areas by scanning the FAT 11. It should benoted that this technique of controlling information on files can be thesame technique as that adopted by a file control system of an ordinarycomputer.

[0077] File system control information including the FAT 11 describedabove is all written into the TOC area before the disc is taken out fromthe signal recording/playback apparatus.

[0078]FIG. 4 is a table showing an example of file system controlinformation. Provided for a file, each entry of the table includesattribute information of the file such as the name of the file (that is,the name of a program stored in the file), a recording date & time, arecording channel, a recording time and a first sector of the file asshown in the figure. When an access is made to a file, the file systemrefers to the entry for the file and starts the access. It is needlessto say that other file attribute information can be added to the table.

[0079]FIG. 5 shows an example of the FAT 11. The example is a table fordata of a program which is not recorded in physically consecutivesectors on the disc. In this case, for each sector storing the data, thenumber of a next sector for storing the same data is recorded. In orderto make the table shown in the figure easy to understand, a free area isrepresented by blanks. In actuality, however, the free area is filled upwith codes “000”. The end of a file is indicated by a code “fff”. Thus,a free area is found by sequentially scanning the left column of the FATstarting from sector 000 and ending at a sector with the next sectorthereof on the right column having a blank (“000”) sector number. Thesize of a free area is found by counting the numbers of physicallyconsecutive sectors included in the free area.

[0080] (b) Searching for a Free Area with a Size Greater than anEquivalent of the 1-Minute Recording/Playback Time Length

[0081] There are 4 methods which can be adopted by the file system forforming a judgment as to whether or not the size of a physicallycontinuous free area is at least an equivalent of the 1-minuterecording/playback time length.

[0082] According to a 1st method, the judgment is formed by determiningwhether or not the free area can be used for accommodating data recordedfor a period of time of at least 1 minute at the maximum recording rate.According to a 2nd method, the amount of data recorded for a 1-minuteperiod of time is first calculated by assuming a fixed recording rate ineach measurement time unit. The recording rate may vary from unit tounit. It should be noted, however that, since the measurement time unititself is also typically 1 minute in length anyway, in actuality, therecording rate can be assumed to be fixed during the 1-minute period oftime. The judgment is then formed by comparing the calculated amount ofdata with the size of the free area. According to a 3rd method, thejudgment is formed by simply determining whether or not the size of thefree area is greater than a predetermined amount of data typicallyexpressed in terms of bytes instead of the amount of data recorded for a1-minute measurement time used in the 2nd method. According to a 4thmethod, the amount of data recorded for a 1-minute period of time isfirst calculated by assuming a fixed recording rate during the 1-minuteperiod of time. In this case, the amount of data resulting from thecalculation is also fixed. The judgment is then formed by comparing thecalculated amount of data with the size of the free area. The 2ndmethod, a representative one among the 4 methods, is explained asfollows.

[0083] In order to implement a fixed recording rate (that is, a fixedencoding bit rate) during the 1-minute period of time prescribed by the2nd method, it is necessary to execute control so that the number ofbits generated by the video encoder which is typically implemented by anMPEG2 encoder in 1 minute is constant.

[0084] A degree of difficulty of carrying out video encoding on apicture is defined as a product of the number of generated bits and anaverage quantization width in 1 picture. In the so-called variable rateencoding process, the number of generated bits is adjusted as follows.In the case of a picture requiring video encoding at a high degree ofdifficulty, encoding needs to be carried out at an encoding bit rategreater than the past average bit rate to allocate a number of generatedbits larger than what would be obtained at the average bit rate in thepast to a complex picture. In the case of a picture requiring videoencoding with a low degree of difficulty, on the other hand, encodingcan be performed at an encoding bit rate smaller than the past averagebit rate to allocate a number of generated bits smaller than what wouldbe obtained at the average bit rate in the past to a simple picture.

[0085] In order to make the rate of generated bits fixed within the1-minute period of time, on the other hand, the actual rate of generatedbits is fed back to be compared with a target value. To put it indetail, if the total amount of code generated in the past is foundsmaller than a product of a target average bit rate and the lapse time,the number of allocated bits is increased. If the total amount of codegenerated in the past is found greater than the product of the targetaverage bit rate and the lapse time, the number of allocated bits isdecreased. As a result, when viewed over along a period of time oftypically 1 minute, recording is still carried out at a fixed bit rateby virtue of an effect provided by the feedback system. At the sametime, a large number of bits and a small number of bits are stillallocated to complex and simple pictures respectively as a result of theapplication of the variable rate encoding process described above,giving rise to an effect that, a characteristic of a variable encodingbit rate for different kinds of picture that enables transmissionwithout sacrificing the quality of the picture is sustained as it is.

[0086] With the variable rate encoding process and the feedback systemapplied as they are, however, there is no assurance that a targetaverage bit rate can be achieved with a very high degree of accuracy. Inorder to solve this problem, an adapted feedback loop with a feedbackgain G shown in FIG. 7 is used. In this feedback loop, the gain G israised approximately before a time of typically 50 seconds lapses sincethe start of the 1-minute period of time, so that the actual totalamount of generated code is forcibly brought to a value equal to theproduct of a target average bit rate and the lapse time. To put itconcretely, the difference between the actual total amount and theproduct at a point of time a 50-second period of time has lapsed sincethe start of the 1-minute period of time is brought to a value within arange ALPHA as shown in FIG. 6 by raising the gain G sometime prior tothe point of time.

[0087]FIG. 8 shows a flowchart representing an encoding process. Asshown in the figure, the flowchart begins with a step S1 at which atarget average encoding bit rate, a maximum encoding bit rate, a minimumencoding bit rate and other parameters such as the range ALPHA are set.

[0088] The flow of the encoding process then goes on to a step S2 toform a judgment as to whether or not a signal being input is the head ofa GOP (Group of Pictures). If the head of a GOP is input, the flow ofthe encoding process proceeds to a step S3 at which the amount ofgenerated code for an I picture is computed. Then, the flow of theencoding process continues to a step S4 at which the number of allocatedbits is computed and the quantization width is adjusted to a valuebetween the maximum and minimum encoding bit rates. In addition, aquantization table is created. Subsequently, the flow of the encodingprocess goes on to a step S5 at which all macroblocks of a picture areencoded. The flow then proceeds to a step S6 at which the number ofgenerated bits is counted. The number of generated bits is used in theadjustment of the quantization width carried out at the step S4. If theoutcome of the judgment formed at the step S2 indicates that the inputsignal is not the head of a GOP, on the other hand, the flow of theencoding process continues directly to the step S5.

[0089] In the encoding process described above, the quantization widthis determined so that the actual amount of generated code can be broughtto a value all but equal to the target code value at the last GOP. Itshould be noted that the number of allocated bits can also be controlledin picture units in place of GOP units. In addition, changing thequantization width is equivalent to manipulating a quantization table (aQ table) in the case of the MPEG encoding.

[0090] 4 Editing

[0091] FIGS. 9 (1) to 9 (5) are diagrams showing layouts of a signalrecorded on the disc of the signal recording/playback apparatus shown inFIG. 1 in a typical editing process.

[0092] In this typical editing process, assume that portion #2 with alength of smaller than the 1-minute recording/playback time length ismoved from its original position in a signal shown in FIG. 9 (1) to apoint of insertion indicated by an arrow by insertion. As the process torewrite the signal due to the insertion of portion #2 is completed, thenew layout of the signal is changed to that shown in FIG. 9 (2). In theinsertion, the process to rewrite portion #1 of the signal behind thepoint of insertion takes a lot of time and labor.

[0093] In order to solve the problem described above, the signal isedited from a layout shown in FIG. 9 (3) to a layout shown in FIG. 9(4). To put it in detail, a continuous free area with a length equal toor larger than the 1-minute recording/playback time length on the discis allocated. In the free area, portion #2 and a part in portion #1 infront of the point of insertion shown in FIG. 9 (1) on the time axis arewritten into the free area to fill up the free area, resulting in thelayout shown in FIG. 9 (4). Assume that the free area is an equivalentof the 1-minute recording/playback time length in length as shown in thelayout of FIG. 9 (3). In this case, the length of the part of portion #1moved to the free area, that is, the length of area A shown in FIG. 9(4), is equal to (the length corresponding to a recording time of1-minute—the length of portion #2). As a result of the work to edit thesignal from the layout shown in FIG. 9 (3) to that shown in FIG. 9 (4),the resulting continuous blocks each have a length greater than anequivalent of the 1-minute recording/playback time length. Thus, seekoperations are carried out at intervals longer than 1 minute, providinga period of time between two consecutive seek operations which is longenough for filling the read buffer memory with data of an amountsufficiently large to be output during a track jump. As a result, aplayback operation can be carried out without a playback time break. Itshould be noted that #1, #2, #3 and #4 in the layout shown in FIG. 9 (5)are consecutive numbers in the time axis direction which correspondrespectively to #1 at the left end, #1 and #2 at the right end, #1 inthe middle and #3 in the layout shown in FIG. 9 (4).

[0094] In the work to edit the signal from the layout shown in FIG. 9(3) to that shown in FIG. 9 (4) described above, area A, the data ofwhich is moved to the free area, is located in front of the point ofinsertion. It should be noted that, however, area A can be locatedbehind the point of insertion. In this case, the data of area A is movedto a location in the free area behind portion #2. As an alternative,area A can comprise 2 sub-areas sandwiching the point of insertion. Inthis case, portion #2 in the free area is sandwiched by 2 pieces of datamoved from the 2 sub-areas of area A respectively.

[0095] 5 Optimization

[0096] Consider a case in which segments #1 to #16 of a signal recordedon the disc are consecutive in the time axis direction but not recordedat physically continuous areas as shown in FIG. 10 (1). The segments canbe rearranged in a so-called defragmentazion process so that they arerecorded at physically continuous areas as shown in FIG. 10 (2). In thiscase, however, it takes a very long time to rearrange the segments assuch and the rearrangement can not be the to be always practical.

[0097] In order to solve the problem described above, in thisembodiment, only segments each with a length of smaller than the1-minute recording/playback time length recorded in scattered areas aretreated as a target of rearrangement in order to make all continuousblocks of the signal at least the equivalent of the 1-minuterecording/playback time length in size. Consider, for example, a signalwith only segment #3 having a length of smaller than the 1-minuterecording/playback time length as shown in FIG. 11 (1). In this case,first of all, a free area with a size of an equivalent of the 1-minuterecording/playback time length is allocated and segment #3 is movedthereto to result in a layout shown in FIG. 11 (2). Then, a portion atthe head of segment #4 with a length equal to (a length corresponding tothe equivalent of the 1-minute recording/playback time length—the lengthof segment #3) is cut out and moved to the free area behind segment #3as shown in FIG. 11 (3) to fill up the free area, resulting in a layoutshown in FIG. 11 (4). Finally, the segment numbers are revised intoconsecutive numbers arranged in an ascending order in the time axisdirection to result in a layout shown in FIG. 11 (5). As shown in FIG.11 (5), the resulting continuous blocks of the signal at their physicallocations on the disc each have a length greater than the equivalent ofthe 1-minute recording/playback time length with the playback orderremaining unchanged. Thus, the number of seek operations is reduced,allowing a playback operation to be carried out smoothly. In this way, afile of a signal on the disc can be optimized with ease.

[0098] 6 Editing Details

[0099] Next, the editing technique shown in FIG. 9 is explained indetail. FIG. 12 is a diagram showing a signal to be edited in theembodiment. As shown in the figure, segments A, C1, C2 and C3 constitutea continuous sequence of data. Assume that segment B is inserted betweensegments A and C1. Let symbols a, c1, b, c2 and c3 denote the lengths ofsegment A, C1, B, C2 and C3 respectively. Editing technique applied to avariety of cases are explained as follows.

[0100] A Lengths a and b Equal to or Larger than the 1-MinuteRecording/Playback Time Length

[0101]FIG. 13 (1) is a diagram showing a case in which segment B to beinserted completes the data at segment C1. Since segments C2 and C3 ofthe signal shown in FIG. 12 do not exist, segment B is merely insertedbetween segments A and C1. However, it is not necessary to physicallymove segments B and C1. What needs to be done is just changing theplayback pointers to A→B→C1. In this case, since segment C1 is thesegment to be played back last, there is no triggered seek operationafter segment C1. Thus, the length c1 of segment C1 can be smaller than1 minute of playback time.

[0102]FIG. 13 (2) is a diagram showing a case in which the datacontinues to segment C3. Even in this case, segment B is just insertedbetween segments A and C1 provided that the length c1 of segment C1 isat least an equivalent of the 1-minute recording/playback time length.That is to say, by merely changing the playback pointers from A→C1→C2→C3to A→B→C1→C2→C3, insertion on the time axis is completed without theneed to physically insert segment B between segments A and C1. In thiscase, the length c2 of segment C2 must be of course at least anequivalent of the 1-minute recording/playback time length as is the casewith the length c1 of segment C1. To be played back last, however, thelength c3 of segment C3 can be smaller than the 1-minuterecording/playback time length.

[0103] Much like FIG. 13 (2), FIG. 13 (3) is a diagram showing a case inwhich the data continues to segment C3. In the latter case, however, thelength c1 of segment C1 is smaller than the 1-minute recording/playbacktime length. Therefore, if segment B is merely inserted between segmentsA and C1, the amount of data temporarily stored in the read buffermemory during the operation to playback segment C1 having a length c1smaller than the 1-minute recording/playback time length will not belarge enough to be used as an output playback signal during a seekoperation accompanying a track jump from segment C1 to segment C2following the operation to playback segment C1 in the playbackoperation. In order to solve this problem caused by the small length c1of segment C1, the data is edited by adopting a technique shown in FIG.13 (4), a diagram showing an editing technique which comprises the stepsof:

[0104] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0105] concatenating segment C1 with a portion at the head of segment C2denoted by notation “C2-(1)” in the figure to form a lump of data havinga size equal to that of the allocated free area; and

[0106] physically relocating the lump of data to the allocated free areato fill up the area.

[0107] It should be noted that, if a free area having a size of at leastan equivalent of the 1-minute recording/playback time length can not beallocated, the editing can not be done and is thus ended unsuccessfully.

[0108] By physically relocating the lump of data in the editingtechnique described above, a seek operation following an operation toplay back a continuous segment having a size smaller than the 1-minuterecording/playback time length can be eliminated provided that theremaining part of segment C2 denoted by notation “C2-(2)” in the figureafter removing the portion at the head of segment C2 denoted by notation“C2-(1)” is at least an equivalent of the 1-minute recording/playbacktime length in size. In this case, the editing work is completedsuccessfully.

[0109] If the remaining part of segment C2 denoted by notation “C2-(2)”is smaller an equivalent of the 1-minute recording/playback time lengthin size, however, the amount of data stored temporarily stored in theread buffer memory to be output as a playback signal during a seekoperation accompanying a track jump from the remaining part of segmentC2 denoted by notation “C2-(2)” to segment C3 will be smaller than the1-minute recording/playback time length. In order to solve this problemcaused by the small length of the remaining part denoted by notation“C2-(2)” of segment C2, the data is edited by adopting a technique shownin FIG. 13 (5), a diagram showing an editing technique which comprisesthe steps of:

[0110] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length behind the relocated portionat the head of segment C2 denoted by notation “C2-(1)”;

[0111] concatenating the remaining part of segment C2 denoted bynotation “C2-(2)” with a portion at the head of segment C3 denoted bynotation “C3-(1)” in the figure to form a lump of data having a sizeequal to that of the allocated free area; and

[0112] physically relocating the lump of data to the allocated free areato fill up the area.

[0113] By physically relocating the lump of data in the editingtechnique described above, a seek operation following an operation toplay back a continuous segment having a size smaller than the 1-minuterecording/playback time length can be eliminated. It should be notedthat, if a free area having a size of at least an equivalent of the1-minute recording/playback time length can not be allocated behind therelocated portion at the head of segment C2 denoted by notation“C2-(1)”, the area originally occupied by segment C2 with a guaranteedsize equal to or larger than the 1-minute recording/playback time lengthcan be used as a free area.

[0114] The editing technique shown in FIG. 13 (5) can be applied tosubsequent segments C4 and C5 if they exist after segment C3.

[0115] B Length a of Smaller than the 1-Minute Recording/Playback TimeLength and Length b Equal to or Larger than the 1-MinuteRecording/Playback Time Length

[0116] In this case, if segment B is merely inserted between segments Aand C1, the amount of data temporarily stored in the read buffer memoryduring an operation to playback segment A having a length smaller thanthe 1-minute recording/playback time length will not be large enough tobe used as an output playback signal during a seek operationaccompanying a track jump from segment A to segment B following theoperation to playback segment A in the playback operation. In order tosolve this problem caused by the small length a of segment A, the datais edited by adopting a technique shown in FIG. 14 (2), a diagramshowing an editing technique which comprises the steps of:

[0117] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0118] concatenating segment A with a portion at the head of segment Bdenoted by notation “B-(1)” in the figure to form a lump of data havinga size equal to that of the allocated free area; and

[0119] physically relocating the lump of data to the allocated free areato fill up the area.

[0120] It should be noted that, if a free area having a size of at leastan equivalent of the 1-minute recording/playback time length can not beallocated, the editing can not be done and is thus ended unsuccessfully.

[0121] By physically relocating the lump of data in the editingtechnique described above, a seek operation following an operation toplay back a continuous segment having a size smaller than the 1-minuterecording/playback time length can be eliminated provided that theremaining part of segment B denoted by notation “B-(2)” in the figureafter removing the portion at the head of segment B denoted by notation“B-(1)”, that is a length {b−(1−a)}, is at least an equivalent of the1-minute recording/playback time length in size. In this case, theediting work is completed successfully. It is thus necessary to form ajudgment as to whether or not the length {b−(1−a)} is at least anequivalent of the 1-minute recording/playback time length or a length(a+b) is at least an equivalent of the 2-minute recording/playback timelength.

[0122] If (a+b) is at least an equivalent of the 2-minuterecording/playback time length in size, the amount of data temporarilystored in the read buffer memory during an operation to playback theremaining part of segment B denoted by notation “B-(2)” will be largeenough to be used as an output playback signal during a seek operationaccompanying a track jump from the remaining part of segment B tosegment C1 following the operation to playback the remaining part ofsegment B in the playback operation. Then, it is necessary to form ajudgment as to whether or not the length c1 of segment C1 is at least anequivalent of the 1-minute recording/playback time length, or whether ornot segment C1 is the last segment of the data. If either of theconditions is satisfied, a seek operation following an operation to playback a continuous segment having a size smaller than the 1-minuterecording/playback time length can be eliminated in which case, theediting work is completed successfully. If both the conditions are notsatisfied, on the other hand, the problem caused by the small length c1segment C1 can be solved by applying a method similar to the editingtechnique shown in FIGS. 13 (3) to (5) of Subsection A with the title“Lengths a and b equal to or larger than the 1-minute recording/playbacktime length” described above.

[0123] To put it in detail, if (a+b) is smaller than the 2-minuterecording/playback time length in size, the problem caused by the smalllength of the remaining part denoted by notation “B-(2)” of segment B issolved by applying an editing technique shown in FIG. 14 (3), a diagramshowing an editing technique of forming a judgment as to whether a freearea having a size equal to or larger than the 1-minuterecording/playback time length can be allocated. If such an area can beallocated, the formation of the judgment is followed by the steps of:

[0124] allocating the free area;

[0125] concatenating the remaining part of segment B denoted by notation“B-(2)” with a portion at the head of segment C1 denoted by notation“C1-(1)” in the figure to form a lump of data having a size equal tothat of the allocated free area; and

[0126] physically relocating the lump of data to the allocated free areato fill up the area.

[0127] If such a free area can not be allocated, on the other hand, thelump area is relocated to the area used to be occupied by segment B. Ineither case, segment B and segment C are fragmented.

[0128] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length (a+b+c1−2) of theremaining part denoted by notation “C1-(2)” of segment C1 after removingthe portion denoted by notation “C1-(1)” is at least an equivalent ofthe 1-minute recording/playback time length, or whether or not theremaining part denoted by notation “C1-(2)” of segment C1 is the lastportion of the data. If either of the conditions is satisfied, a seekoperation following an operation to play back a continuous segmenthaving a size smaller than the 1-minute recording/playback time lengthcan be eliminated in which case, the editing work is completedsuccessfully. If both the conditions are not satisfied, on the otherhand, the problem caused by the small length of the remaining partdenoted by notation “C1-(2)” of segment C1 can be solved by applying anediting technique shown in FIG. 14 (4), a diagram showing an editingtechnique which comprises the steps of:

[0129] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0130] concatenating the remaining part of segment C1 denoted bynotation “C1-(2)” with a portion at the head of segment C2 denoted bynotation “C2-(1)” in the figure to form a lump of data having a sizeequal to that of the allocated free area; and

[0131] physically relocating the lump of data to the allocated free areato fill up the area.

[0132] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “C2-(2)” of segment C2 after removing the portiondenoted by notation “C2-(1)” is at least an equivalent of the 1-minuterecording/playback time length, or whether or not the remaining partdenoted by notation “C2-(2)” of segment C1 is the last portion of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifboth the conditions are not satisfied, on the other hand, the problemcaused by the small length of the remaining part denoted by notation“C2-(2)” of segment C2 can be solved by applying an editing techniqueshown in FIG. 14 (5), a diagram showing an editing technique whichcomprises the steps of:

[0133] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0134] concatenating the remaining part of segment C2 denoted bynotation “C2-(2)” with a portion at the head of segment C3 denoted bynotation “C3-(1)” in the figure to form a lump of data having a sizeequal to that of the allocated free area; and

[0135] physically relocating the lump of data to the allocated free areato fill up the area.

[0136] C Length a Equal to or Larger than the 1-MinuteRecording/Playback Time Length and Length b Smaller than the 1-MinuteRecording/Playback Time Length

[0137] In order to solve this problem caused by the small length b ofsegment B, the data is edited by adopting a technique shown in FIG. 15(2), a diagram showing an editing technique which comprises the stepsof:

[0138] allocating a free area having a size of (1−b) right behindsegment B; and

[0139] relocating a portion at the head of segment C1 denoted bynotation “C1-(1)” in the figure to fill up the free area.

[0140] As an alternative, the technique may comprise the steps of:

[0141] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0142] concatenating the segment B with the portion at the head ofsegment C1 denoted by notation “C1-(1)” in the figure to form a lump ofdata having a size equal to that of the allocated free area; and

[0143] physically relocating the lump of data to the allocated free areato fill up the area.

[0144] It should be noted that, if a free area having a size of at leastan equivalent of the 1-minute recording/playback time length can not beallocated in either case, the editing can not be done and is thus endedunsuccessfully.

[0145] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “C1-(2)” of segment C1 after removing the portiondenoted by notation “C1-(1)” is at least an equivalent of the 1-minuterecording/playback time length, or whether or not the remaining partdenoted by notation “C1-(2)” of segment C1 is the last portion of thedata, that is, whether or not segment C1 is the last segment of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifboth the conditions are not satisfied, on the other hand, the problemcaused by the small length of the remaining part denoted by notation“C1-(2)” of segment C1 can be solved by applying editing techniquesshown in FIGS. 15 (3) and 15 (4) which are similar to those shown inFIGS. 13 (4) and 13 (5) described earlier respectively.

[0146] D Both Lengths a and b Smaller than the 1-MinuteRecording/Playback Time Length

[0147] In this case, editing work for a total length (a+b) equal to orlarger than the 1-minute recording/playback time length is differentfrom that for a total length (a+b) smaller than the 1-minuterecording/playback time length. The following description begins with acase shown in FIG. 16 (1) in which the total length (a+b) is smallerthan the 1-minute recording/playback time length. The case requires atechnique shown in FIG. 16 (2), a diagram showing an editing techniquewhich comprises:

[0148] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0149] concatenating segments A and B with a portion at the head ofsegment C1 denoted by notation “C1-(1)” in the figure to form a lump ofdata having a size equal to that of the allocated free area; and

[0150] physically relocating the lump of data to the allocated free areato fill up the area.

[0151] As an alternative, the editing technique may comprise the stepsof:

[0152] allocating a free area having a size of (1−b) right behindsegment B; and

[0153] physically relocating a portion at the head of segment C1 denotedby notation “C1-(1)” in the figure to fill up the free area.

[0154] It should be noted that, if a free area having a size of at leastan equivalent of the 1-minute recording/playback time length can not beallocated in either case, the editing can not be done and is thus endedunsuccessfully.

[0155] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “C1-(2)” of segment C1 after removing the portiondenoted by notation “C1-(1)” is at least an equivalent of the 1-minuterecording/playback time length, or whether or not the remaining partdenoted by notation “C1-(2)” of segment C1 is the last portion of thedata, that is, whether or not segment C1 is the last segment of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifboth the conditions are not satisfied, on the other hand, the problemcaused by the short length of the remaining part denoted by notation“C1-(2)” of segment C1 can be solved by applying an editing techniquesshown in FIGS. 16 (3) and 16 (4) which are similar to those shown inFIGS. 13 (4) and 13 (5) described earlier respectively.

[0156] The following is description of a case shown in FIG. 17 (1) inwhich the total length (a+b) is at least an equivalent of the 1-minuterecording/playback time length. In this case, it is necessary to apply atechnique shown in FIG. 17 (2), a diagram showing an editing techniquewhich comprises:

[0157] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0158] concatenating segment A with a portion at the head of segment Bdenoted by notation “B-(1)” in the figure to form a lump of data havinga size equal to that of the allocated free area; and

[0159] physically relocating the lump of data to the allocated free areato fill up the area.

[0160] It should be noted that, if a free area having a size of at leastan equivalent of the 1-minute recording/playback time length can not beallocated in either case, the editing can not be done and is thus endedunsuccessfully.

[0161] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “C1-(2)” of segment C1 after removing the portiondenoted by notation “C1-(1)” is at least an equivalent of the 1-minuterecording/playback time length, or whether or not the remaining partdenoted by notation “C1-(2)” of segment C1 is the last portion of thedata, that is, whether or not segment C1 is the last segment of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifboth the conditions are not satisfied, on the other hand, the problemcaused by the short length of the remaining part denoted by notation“C1-(2)” of segment C1 can be solved by applying an editing techniquesshown in FIGS. 17 (4) and 17 (5) which are similar to those shown inFIGS. 13 (4) and 13 (5) described earlier respectively.

[0162] In the cases discussed in subsections A to D, segment B to beinserted is recorded in one continuous area. The following subsectionsdescribe cases in which segment B comprises sub-segments B1, B2 and B3which are recorded in areas physically separated from each other. It isassumed that, as a single segment, there is an assurance that data ofsegment B can be reproduced without generating a playback time breakcaused by a seek operation which is in turn attributed to a track jump.That is to say, sub-segments B1 and B2 each have a length equal to orlarger than the 1-minute recording/playback time length. To be playedback last, on the other hand, sub-segment B3 can be at least or smallerthan the 1-minute recording/playback time length in size.

[0163] E Both Lengths a and b (=b1+b2+b3) Equal to or Larger than the1-Minute Recording/Playback Time Length

[0164] Processing for a case in which sub-segment B3 has a length b3equal to or larger than the 1-minute recording/playback time length isdifferent from a case with the length b3 smaller than the 1-minuterecording/playback time length. In the former case shown in FIG. 18 (1),it is necessary to form a judgment as to whether or not the length c1 ofsegment C1 is at least an equivalent of the 1-minute recording/playbacktime length or whether or not segment C1 is the last segment of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully bymerely correcting the playback pointers. If both the conditions are notsatisfied, on the other hand, the problem caused by the short length ofsegment C1 can be solved by applying an editing techniques shown inFIGS. 18 (2) and 18 (3) which are similar to those shown in FIGS. 13 (4)and 13 (5) described earlier respectively.

[0165]FIG. 19 (1) is a diagram showing a case in which the length b3 ofsub-segment B3 is smaller than the 1-minute recording/playback timelength. In this case, it is necessary to apply a technique shown in FIG.19 (2), a diagram showing an editing technique which comprises:

[0166] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0167] concatenating sub-segment B3 with a portion at the head ofsegment C1 denoted by notation “C1-(1)” in the figure to form a lump ofdata having a size equal to that of the allocated free area; and

[0168] physically relocating the lump of data to the allocated free areato fill up the area.

[0169] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “C1-(2)” of segment C1 after removing the portiondenoted by notation “C1-(1)” is at least an equivalent of the 1-minuterecording/playback time length, or whether or not the remaining partdenoted by notation “C1-(2)” of segment C1 is the last portion of thedata, that is, whether or not segment C1 is the last segment of thedata. If either of the conditions is satisfied, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifboth the conditions are not satisfied, on the other hand, the problemcaused by the short length of the remaining part denoted by notation“C1-(2)” of segment C1 can be solved by applying an editing techniquesshown in FIGS. 19 (3) and 19 (4) which are similar to those shown inFIGS. 13 (4) and 13 (5) described earlier respectively.

[0170] F Length a of Smaller than the 1-Minute Recording/Playback TimeLength and Length b (=b1+b2+b3) Equal to or Larger than the 1-MinuteRecording/Playback Time Length

[0171]FIG. 20 (1) is a diagram showing a case in which the length a issmaller than the 1-minute recording/playback time length and the lengthb (=b1+b2+b3) is at least an equivalent of the 1-minuterecording/playback time length. In this case, it is necessary to apply atechnique shown in FIG. 20 (2), a diagram showing an editing techniquewhich comprises:

[0172] allocating a free area having a size of at least an equivalent ofthe 1-minute recording/playback time length;

[0173] concatenating segment A with a portion at the head of sub-segmentB1 denoted by notation “B1-(1)” in the figure to form a lump of datahaving a size equal to that of the allocated free area; and

[0174] physically relocating the lump of data to the allocated free areato fill up the area.

[0175] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “B1-(2)” of sub-segment B1 after removing theportion denoted by notation “B1-(1)” is at least an equivalent of the1-minute recording/playback time length. If the remaining part denotedby notation “B1-(2)” of sub-segment B1 is at least an equivalent of the1-minute recording/playback time length in length, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifthe remaining part denoted by notation “B1-(2)” of sub-segment B1 issmaller than the 1-minute recording/playback time length in length, onthe other hand, it is necessary to apply a technique shown in FIG. 20(3), a diagram showing an editing technique which comprises:

[0176] allocating a free area having a size equal to or larger than the1-minute recording/playback time length;

[0177] concatenating the remaining part denoted by notation “B1-(2)” ofsub-segment B1 with a portion at the head of sub-segment B2 denoted bynotation “B2-(1)” in the figure to form a lump of data having a sizeequal to that of the allocated free area; and

[0178] physically relocating the lump of data to the allocated free areato fill up the area.

[0179] After the lump of data has been relocated, it is necessary toform a judgment as to whether or not the length of the remaining partdenoted by notation “B2-(2)” of sub-segment B2 after removing theportion denoted by notation “B2-(1)” is at least an equivalent of the1-minute recording/playback time length. If the remaining part denotedby notation “B2-(2)” of sub-segment B2 is at least an equivalent of the1-minute recording/playback time length in length, a seek operationfollowing an operation to play back a continuous segment having a sizesmaller than the 1-minute recording/playback time length can beeliminated in which case, the editing work is completed successfully. Ifthe remaining part denoted by notation “B2-(2)” of sub-segment B1 issmaller than the 1-minute recording/playback time length in length, onthe other hand, it is necessary to repeat the processing described abovefor the remaining part denoted by notation “B2-(2)” of sub-segment B2and sub-segment B3.

[0180] In the editing techniques described above, the minimum size of acontinuous segment is set at a value equivalent to the 1-minuterecording/playback time length. It should be noted that this value canbe changed depending on the seek time, the rotation wait time and thesettle time of the signal playback apparatus. For example, the minimumsize of a continuous segment is set at a multiple or a fraction of theequivalent of the 1-minute recording/playback time length. In addition,the minimum size of a continuous segment can be set in dependence onfactors other than the time related parameters. To be more specific, theminimum size of a continuous segment can be set at an equivalence of apredetermined amount of data, the GOP unit used in the MPEG encodingprocess or a data unit used in internal processing such a packet or ablock.

[0181] As described in detail above, according to the present invention,the amount of data stored in advance in the read buffer memory duringthe time is large enough to eliminate a next playback time break, thatis, to be output during a next track jump in a seek operation entailingnot only a seek time, but also a rotation wait time and a settle time.As a result, the eventual playback signal can be generated continuously.In addition, the time it takes to optimize data recorded in the disc bydefragmentazion of the data can be reduced substantially.

What is claimed is:
 1. A signal recording method whereby, in anoperation to record a signal onto a recording medium, said signal isrecorded in continuous free areas each having a size equal to or largerthan a predetermined recording/playback time length.
 2. A signalrecording/playback method wherein, in an operation to insert anadditional signal having a length smaller than a predeterminedrecording/playback time length into a point of insertion in an area on arecording medium already occupied by an existing signal, said signalrecording/playback method is implemented by executing the steps of:newly allocating a continuous free area on said recording medium with asize of at least said equivalence of said predeterminedrecording/playback time length to said additional signal; recording saidadditional signal in said continuous free area; and filling up the restof said continuous free area with a portion of said existing signaladjacent to said point of insertion.
 3. A signal recording/playbackmethod wherein, in case a signal already recorded on a recording mediumhas a continuous segment smaller in size than an equivalence of apredetermined recording/playback time length, said signalrecording/playback method is implemented by executing the steps of:newly allocating a continuous free area on said recording medium with asize of at least said equivalence of said predeterminedrecording/playback time length to said segment; relocating said segmentto said continuous free area; and filling up the rest of said continuousfree area with a portion of said signal adjacent to said segment.
 4. Asignal recording apparatus for recording a signal onto a recordingmedium, said apparatus comprising: a 1st means for recognizing acontinuous free area on said recording medium with a size equal to orlarger than a predetermined recording/playback time length; and a 2ndmeans for executing control to record a signal onto said continuous freearea.
 5. A signal recording/play back apparatus for recording andplaying back a signal onto and from a recording medium, said apparatuscomprising: a 1st means for recognizing a continuous free area on saidrecording medium with a size equal to or larger than a predeterminedrecording/playback time length; and a 3rd means for executing control torecord a signal, which is supposed to be newly inserted into a point ofinsertion in an area on said recording medium already occupied by anexisting signal, onto said continuous free area and to fill up the restof said continuous free area with a portion of said existing signaladjacent to said point of insertion.
 6. A signal recording/play backapparatus for recording and playing back a signal onto and from arecording medium, said apparatus comprising: a 1st means for recognizinga continuous free area on said recording medium with a size equal to orlarger than a predetermined recording/playback time length; and a 4thmeans for executing control to relocate a continuous segment of a signalalready recorded on said recording medium having a size smaller than apredetermined recording/playback time length and to fill up the rest ofsaid continuous free area with a portion of said already recorded signaladjacent to said segment.
 7. A signal recording medium wherein a signalis recorded into continuous areas each having a size equal to or largerthan a predetermined recording/playback time length.